Means for eliminating magnetic coupling



Jan. 8, 1929. 1,698,364

L. A. HAZELTINE Original Filed April 7, 1924 2 Sheets-Sheet 1 INVENTOR [00/5 Af/azell'me ATTORNEYS Jan. 8, 1929.

- L. A. HAZELTINE MEANS FOR summ'rme MAGNETIC COUPLING Original Filed A ril 7, 192A 2 Sheets-Sheet 2 -{Ill lllll'll i- R I a INVENTOR 100/15 4. flazelflhe ATTORNEYS Patented Jmfs, 1929.

UNITED STATES PATENT OFFICE.

Louis a. EAZELTINE, or nonoxEN, NEW JERSEY, nssrenoa 'ro HAZELTINE conrona- TION, a CORPORATION 0E DELAWARE.

ms FOB- ELIIHTATHTG IAGNETIC COUPLING.

Original application died April 7, 1924,8er1a1 No. 704,628.

Divided and this application flied June 30, 1925.

This invention relates to wave signaling systems, particularly radio and high-frequency carrier-current or line-radio employing a plurality of coils, and has for its object the provision of means for, the elimination of undesirable magnetic coupling between such coils, and further objects hereinafter to be described. s For many electrical purposes, particularly in radio communication systems, it is common to employ coils having an open magnetic circuit of non-magnetic material. The simplest and most readily constructed coil is circular,

- i. e. all of its turns are coaxial circles except for the effect of the winding pitch. The cur-.

rent in such a coil produces a magnetic flux extending a distance in all directions and in general linking with other. coils that may be in the neighborhood, thus 'ving rise to magnetic coupling 1 between t. e coils. To avoid such magnetic. coupling between two coils, it has been customary to mount them with the axis of one lyin in the midplane of the other, the two axes eing at right angles. Three coils can be mounted in this way so that there is no coupling between any two, but this result cannot be attained with more than three coils, because no more than three directions mutually at right angles exist in three-dimensional space. Further, this method of mounting is not convenient, as each coil must be mounted in a diiierent manner. Another disadvantage is due to the fact that each coil roduces a magnetic field in a difierent direction and so makes diflicult the elimination of magnetic couplin s between one or more of the coils with ot er portions of adjacent circuits or apparatus. 'An additional method ofavoiding magnetic coupling.

is to enclose each coil completely in a metal compartment or shield,-but this more complicated construction is usually not desired because of increased weight and cost and because such shields frequently introduce undesired capacity couplings, and, in addition, introduce eddy-current loss in the metal.

The present invention is shown in its preferred embodiment as being utilized in 'con,

nection with a radio receiver employing two Patent No. 1,577,421, dated March 18, 1928.

Serial No. $0,488.

stages of tuned radio-frequency amplification 5 and a detector, the undesirable capacity coupling between the grid and plate electrodes of the amphfym tubes being neutralized according to azeltine U. S. Patents Nos. 1,489,228 and 1,533,858. The invention is of particular value when utilized in such a circult arrangement because, in order to obtain the maximum benefit from capacity coupling neutralization, it is necessary that interstage magnetic coupling be eliminated except, of 5 course, for the desired coupli in each transformer. The facility with which undesirable magnetic coup ing between intersta e radiofrequency transformers may be eliminated through. the agency of the present invention therefore makes it especially applicable to, radio receivers of the type mentioned.

Improved method and means for eliminatmg magnetic coupling between coils'without intro ucing the objections mentioned aboveare described in Ha-zeltine U. S. Patent No. 1,577,421, issued March 16, 1926, of which this application is a division, wherein it is demonstrated that if any number of coils be arranged in a row, the axes of the coils being in thesame plane and similarly inclined to a common reference'line intersecting the coils, magnetic coupling between the coils may be substantially eliminated. That invention is especially applicable to radio receiving apparatus employing successive tuned circuits, wherein it is customary to employ coils each one being tuned by an as sociated variable condenser.

It is explained in the ap lication last referred to that in order to o tain the advan-. tages of that invention, itis' necessarythat the coils, between which there would otherwise be undesirable magnetic coupling,=be placed so that the centers of the coils lie in the same straight line, with the axes parallel and at an angle of approximately 55 to the line of centers of the coils. In addition, it is stated that it is necessary to make as short as possible the leads connecting eachetransformer or coil with its associated tuning condenser; the reason for the latter requirement being that loops formed by connecting leads,

if more than a few inches in length, are likely to set up conflicting stray magnetic fields and to introduce stray capacity couplings which may seriously interfere with the desired elimination of coupling as described.

The present invention provides simple and eficient means for obtaining the full advan tages of the invention referred to by provida tuning unit comprising a coil and tuning condenser so associated as to be mechanically strong and electrically efficient. By thus mounting each coil rigidly upon its tuning conden er, which in turn may be secured to a panel, as illustrated in the drawings, the coils may readily be placed automatically at the correct angle to eliminate undesired magnetic coupling in the manner described, with e assurance that this angle will be permanently maintained. In addition, this unit introduces other improvements which will now be described in detail.

Referring to the drawings,

1 illustrates a detail side view of a condenser-transformer tuning unit;

Fig. 2 is a top view of a radio receiver conling three tuning units substantially simna "to that shown in Fig. l; and

3 is a circuit diagram of a complete radio receiver, a view of which is given in 2. lieferringto Fig. 1, there is illustrated a bl-e air condenser 1, which, by means of brackets 2 and 8, supports transformer This transformer comprises primary inding 4E closely coupled to a secondary ding 5, the variable condenser being here nee-ted in parallel with the secondary iding. This tuning unit is complete in and may be rapidl assembled accorde" to standardized speci cations. In assemradio receivers, of which Figs. 2 and 3 nustrative of but one example, two or e units such as shown in Fig. 1 may readbe mounted upon the control panel 6 of receiver at the proper angle, previously urting holes which preferably should have n drilled with theaid of a template. It will thus be appreciated thatvby arranging he tuning units as shown, the correct angle eliminating undesirable magnetic cou- 7 ng may be arrived at with minimum labor, because the placing of the condenser-coil units all on the same panel will automatically cats the coils with their centerson the same straight line and with their axes at approximately the correct angle to that line, the only additional adjustment being a small one vnich may be made during the final testing the receiver, such as by moving the brackate :2 and 8 inthe proper direction beneath the retaining nuts 7, Fig. 1. The primary cirsuits in which these units may be included usually have relatively small capacities, and J the primary coils much fewer turns than the erred to, by means of suitably located messea secondary coils, hence the radio-frequency currents in the primary circuit have a very small magnetic effect as compared with the radio-frequency currents in the secondaries. It is therefore the secondary coils which articularly should have zero magnetic coup ing.

Furthermore, by mounting the coils on the back of the variable condensers through the agency of short brackets 2 and 8, the coils are securely held in'a position which allows of extremely short connecting leads between the coil and the tuning condenser, thus eliminating possible magnetic loops, and likewise reducing possible capacity couplings between stages. These short leads are represented in Fig. l by-insulated wire 9 and bracket 8, the latter serving both as a support and an electrical conductor. The condenser plates are thereby also placed in such a position relative to the magnetic field of the coils that a minimum eddy-current loss results.

Tuning units as described herein are of advantage not only from the standpoint of commercial practice, wherein the factory assembly of receivers is greatly facilitated, but in addition are of great value to the amateur constructor who is thus enabled to procure a complete tuning element comprising a variable condenser with a single coil, or transformer including a plurality of coils, which has been accurately designed for efficient operation, and allows of compact assembly and simplicity of external connections.

Itwill be readily understood that the merits of this invention are applicable with equal value to single coils and multi-coil transformers as illustrated herein, as well as to coils or transformers of non-cylindrical shape such as so-called basket-weave, pan-cake and other special forms of coils.

It will also be understood that the term panel as employed in the appended claims may be defined as any common support upon which the tuning units may be mounted.

I claim:

1. A. physically compact unit adapted to tune at least one oscillatory circuit of a wave signaling device, comprising a variable condenser having mounted thereon an inductance coil connected to said condenser, said condenser including a plurality of plates, said coil being secured in close proximity to said condenser and so positioned relative thereto that the magnetic fieldof said coil produces substantially a minimum of eddy currents in said plates. p

2. In a radio receiver a plurality of condenser-coil units each adapted to tune atleast one radio-frequency circuit thereof, each of said units comprising a variable tuning condenser and an inductance coil, said coil being disposed in such close proximity to said condenser as to permit of short conducting leads for interconnecting said coil with said condenser, thereby minimizing undesired reac denser by supportingmeans which so or ien-- tate said transformers in their relation to n tions between said units resulting from the magr eticand electrostatic couplings between the leads of one unit and those of another, said condensers being mounted in a row on a common supporting panel and said coils being mounted upon said condensers by supporting means'such that said coils are so orientated with respect to each other that'there is substantially zero magnetic coupling between them.

3. In a radio receiver including a multistage tuned radio-frequency amplifier, a plu rality of tunable interstage coupling units each comprising a coupling transformer and a tuning condenser combined to form a selfcontained unitary structure in which the transformer is mounted upon and supported by the condenser and is electrically connected therewith by short leads, whereby undesired stray capacity and magnetic couplings are minimized, said unitary structures being identical and all mounted in a row on a common supporting panel, the magnetic centers of said transformers being disposed substantially in a straightline, and the magnetic axis of each of said transformers being disposed at an angle of approximately '55 to said straight line, whereby there is substantially zero magnetic coupling between said transformers.

4. In a radio receiver including a multistage tuned radio-frequency amplifier, the combination of a panel and a plurality oftuning units mounted thereon in a straight line, each unit including an inductance coil and a variable tuning condenser combined to form a self-contained unitary structure in which the coil is mounted upon the condenser by supporting means, said means effecting an orientation of said coils in relation to their respective condensers such that there is substantially zero magnetic coupling between said coils.

5. In a radio receiver, a multi-stage tuned radio-frequenc amplifier including a plurality of tuna le interstage couplingunits mounted on a panel in a straightline, each unit including a coupling transformer and a variable tuning condenser combined to form a self-contained unitary structure in which the transformer is mounted upon the contheir respective condensers and to each other that there is substantially zero magnetic coupling between said transformers.

. 6. A self-contained unitary structure comprising'a variable tuning condenser and a coupling transformer attached to and supported by saidcondenser, said condenser including a rotatable operating shaft carrying condenser plates, the magnetic'axis of said coupling transformer being disposed sub-.

stantially parallel to said plates, whereby a losses occur in said plates, the orientation of the transformer and condenser of said structure being such that the mounting in combination of a plurality of unitary structures, as above defined, upon a supporting panel, in a straight line, and with the axes of said operating shafts parallel to each other results in the substantial elimination of magnetic coupling between said transformers.

8. A self-contained unitary structure a rotatable operating plates whereby a minimum of eddy-current adapted to be mounted upon a panel, said structure comprising a variable tuning condenser and a con ling transformer attached to and supporte by said condenser, said condenser including a rotatable operating shaft carrying condenser plates, the magnetic axis of said coupling transformer being dis- I posed substantially parallel to said plates whereby a minimum of eddy-current losses occurs in said'plates, the orientation of the transformer and condenser of said structure being such that the mounting in combination of a plurality of unitary structures, as above defined, upon a supporting anel, in a straight line, with the axes of said operating shafts parallel to each other, with the magnetic axes of said transformers parallel to each other and similarly inclined-with re spect to a straight line passing .thru their magnetic .centers, results in the substantial elimination of magnetic coupling between said transformers.

9. In a radio receiver including a multistage tuned radio-frequency amplifier, the

combination of a. plurality of tuning units mounted in a row upon a common support, each unit including an inductance coil and a variable tunin condenser combined to form a self-contained-unitary structure, in which the coil is mounted upon the condenser bysupporting means, said condensers being similarly secured to said support, said supporting means effecting an orientation of said coils in relation to their respective condens ers and to each other, such that there is substantially zero magnetic coupling between said coils.

10. In a radio receiver, a multi-stage tuned radio-frequenc amplifier including a plurality of tuna le interstage coupling units mounted in a row upon a common support,

neessee each unit including a coupling transformer and a variable tuning condenser combined to form a self-contained unitary structure in "which the transformer is mounted upon the condenser by supporting means, said condensers being similarly secured to said support, said supporting means eflecting an orientation of said transformers in relation to their respective condensers and to each other such that there is substantially zero 1 magnetic coupling between said transformers.

In testimony whereof I afiix my signature.

LOUIS A. HAZELTINE". 

